360 M. Ehrenberg on Uncri/stallized Mineral Substances. 



of saffron-yellow, is all at once transformed into dendritic crystals of 

 deep-red, and which Professor Erdmann has recently prepared with the 

 chloro-arseniate of potass and the acetate of lead. This salt shews us the 

 finest example of these singular metamorphoses. It must therefore be 

 considered as demonstrated, that crystals neither exist nor can exist 

 without a previous mechanical crystalloidal deposition of particles. 



It is not our purpose here to inquire, whether all these phenomena arc 

 owing- to the general force of attraction, or, whether, as Mr Faraday has 

 alleged with some reason, electricity be not the most general principle 

 which regulates chemical and magnetological actions, and even many of 

 those of vegetable and animal life ; but when we can here recognise one 

 of the modifications of the general force which regulates the formation of 

 bodies in crystallization, we may well likewise admit a crystalloidal or 

 morpholitic force. My design, however, has principally been to draw 

 attention to these singular phenomena and their relations, and to shew, 

 that at times crystalloidal structures must exercise a considerable influ- 

 ence in the formation of masses of friable rocks which have not reached the 

 point of crystallization. 



I have likewise been led to the discovery of a solid centre of compo- 

 sition in the structure of isolated rings. After many researches, I suc- 

 ceeded in discovering this in sulphur. When oil is poured on flowers of 

 sulphur, we often see crystals of sulphur separate themselves around the 

 granules, while the granules disappear. In other instances, masses of 

 dendritic or linear crystals arc formed, which afterwards constitute iso- 

 lated crystals. In many other circumstances besides, we see a cloudy 

 concentric halo, broad and interrupted, appear round each granule, 

 which afterwards produces a crystal. The appearance en lunette is pro- 

 duced when two granules approach each other with equal force. Per- 

 haps one might succeed, by observing the relations which similar crys- 

 tallizations present when they proceed slowly, in discovering other in- 

 teresting phenomena; but it was not till after man}' trials, that I managed 

 to observe in a state of activity, the rapid and elegant crystallization of 

 salts, and to watch the formation of a siliceous sphere going on under my 

 e3'es. Does the difficulty consist in the extreme minuteness, or the trans- 

 parency of the elementary parts, or rather in the absence of these proper- 

 tics, or, lastly, in the rapidity with which the operation takes place ? 



Speculations as to the Primary Source of the Carbon and 

 Nitrogen present in Plants and Animals. By Charles 

 Daubeny, M.D., F.R.S., &c. &c* 



Dr Daubeny says: I cannot refrain from calling attention to the fact, 

 that carbonic acid and ammonia, which have been shewn to be the sources re- 

 spectively of the carbon and the nitrogen of plants, on the one hand exist in 



* The interesting speculations of Dr Daubeny here given are extracted from 

 the Doctor's valuable Lectures en Agriculture just published. Long before the 



